问题已解决，在eclipse的项目处右键单击，选择run as->java application 就可以运行了。感谢各位大神的指教。
以下是原问题：
当用eclipse运行以下代码时出现错误。请各路大神看看怎么回事
package test;
public class Test {
public static void main(String[] args) {
// TODO Auto-generated method stub
}
}
错误：Exception in thread "main" java.lang.Error: Unresolved compilation problems:
ProcessFiles cannot be resolved to a type
The method print(String) is undefined for the type AtUnit
The method print(String) is undefined for the type AtUnit
The method print(String) is undefined for the type AtUnit
The method print(String) is undefined for the type AtUnit
at atunit.AtUnit.main(AtUnit.java:19)
